There is a need for an exposure instrument that is cost-effective and can directly measure the toxicity of the air in real time. This capability is needed to understand the negative impact on health that occurs in real world exposures to multiple pollutants in both gasses and particles. This is a recognized emerging need in air quality risk assessment. The objective of this study is to improve the toxicity detection limitof an existing exposure instrument to directly measure toxicity of the air from particulate matter (PM) concentrations of 1,000 g/m3 down to an atmospherically relevant 50 g/m3. Our patented exposure instrument, named the Gillings device, is innovative because it is already able to directly measure the toxicity of air in a cost-effective technology. The Gillings device creates direct exposures to living cultured human lung cells to gases and particles without pre-collection or the use of solvents. This is accomplished through electrostatic charging that efficiently deposits particles directly onto living cells simulating real-world exposures and increasing sensitivity by 16-fold. The electrostatic charging does not harm the living tissue, yet is still effective in collecting an depositing particles onto the cells for in vitro determination of a wide range of toxicological endpoints. A major advantage of the Gillings device is that sampling artifacts are vastly reduced compared to exposure methods of filtration and resuspension, gravitational settling, or impaction. We have already shown in PM exposures of 1,000 g/m3 the Gillings device is able to deposit 4 g/cm2 of PM directly to living human lung epithelial cells resulting in a 3-fold increase of inflammatory markers over control air streams. These exposure concentrations are too high to be used in real-world environments and thus modifications are needed to improve deposition efficiency for exposures of 50 g/m3. If this were successful we could use the device to target academic and government research, outdoor air quality monitoring, and industrial manufacturing indoor monitoring with a total addressable market estimated to be $1.2 billion annual sales (2011) and growing at a rate of >9% (data from purchased market research studies, e.g., from Frost & Sullivan and BCC group). The completion of phase I will result in data demonstrating the feasibility of the Gillings device to sample real-world environments. In phase II we will target researchers in the academic community as beta testers of the device and iteratively refine the device into a more compact and robust system with increased features for ease of use. These improvements will permit the expansion of the target market to include regulatory and defense government agencies, and industry users such as pharmaceutical manufacturers and product testers.